<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // 判断质数 看不懂啊
        var num = prompt("输入数字");
        for (var i = 2 ; i <= num/2 ;i++ ) {
            if(num % i == 0){
                alert('g');
                break;
            }else{
                alert(num);
                break;
            }
         }
    </script>
</body>
</html>